The objective of this work is to examine the role of attenuation in the regulation of gene expression for isoleucine/valine biosynthesis in Escherichia coli K12. We have established the DNA sequence for the promoter-attenuator region of the ilvGEDA operon. We propose to (1) isolate mutations within this region; and (2) correlate the effect of these mutations on gene expression by biochemical analysis and DNA sequencing. This will contribute directly to our understanding of attenuation and enhance our understanding of overall gene expression.